Nails are some of the oldest connecting means known in construction technology such as house building, ship building, armaments technology etc., mostly in connection with wood as a material. A basic distinction should be made between rigid and hard nails made of metal, mostly iron/steel, which are driven directly into wood by hammering, and wooden nails that require a bore hole in order to connect two or more components made of wood or other materials, such as e.g. leather, to one another. Without a bore hole the wooden structures are crushed and/or the wooden nails break and/or shatter when struck with the hammer.
Traditionally nails are driven into the material to be nailed with hammers. Generally, a number of hammer blows are required for this purpose, there being a risk of bending the nail if the head of the nail is not struck in the longitudinal extension of the nail shaft.
Since with increasing industrialisation production speed is becoming more and more important for financial reasons, tools have been developed with which nails can be driven into the components to be connected more quickly than with a handheld hammer. These include in particular nail drivers which can be equipped with different drive concepts, compressed air playing a prominent role. Pneumatic nail guns are generally operated at pressures of 5-6 bar. The thrust speed is on average approx. 46 m/s (http://blogs.cdc.gov/niosh-service-blog/2013/07/16/nail.gun-comic/). Alternatively, nails can also be driven in with propelling charges. Speeds of 96 m/s to 395 m/s can be set here (http://en/wikipedia/org/wiki/Powder-actuated_tool).
In order to increase processing speeds, nails are combined to form rigid or flexible strips of nails which, when applying nails, can be used for automatically reloading a new nail in the nail driver. In addition to many advantages, steel nails also have some disadvantages. Despite corrosion prevention measures, such as galvanising, steel nails have a tendency to rust under ad-verse conditions. This is particularly the case if acid conditions prevail in the material being nailed. This applies in particular to woods with a high tanning agent content (hardwoods such as oaks, Bangkirai, or softwoods such as pines, Douglas fir, larch, etc.) which, due to their longevity in outdoor areas, are used e.g. for facades or terraces. When weathered, undesirable dark to black discolouration occurs, e.g. drip projections on facades at the nailing points. It is possible to remedy this by using stainless steel types, but it is very expensive.
Another disadvantage of steel nails relates to their recycling. Nailed wood is generally not processed with wood processing tools because tool blades be-come blunt very quickly or may be destroyed if they strike steel nails. Wooden components that contain steel nails are therefore mostly reduced into particles using crushers and are cleansed of any steel and iron components by means of magnets in order to be used for the production of chipboard or for fuel.
In some applications the interaction of iron or metals with electromagnetic waves is also undesirable. Thus, components that contain metal cannot be treated with high-frequency electromagnetic waves, e.g. with microwaves. Metal-free nails that do not cause any discoloration, in particular when weathered, can be processed by wood processing machines without damaging the tools and are electromagnetically compatible, and so have an interesting market potential. As well as facade applications, e.g. temporary structures such as hoardings, shuttering etc. or packaging can be connected with metal-free nails, and after use can be broken down into their components for material recycling by machining tools (e.g. saws). In this connection it is known from JP9043171 and U.S. Pat. No. 5,547,325A to use nails made of reinforced plastic or glass fibre-reinforced high performance plastics.
However, the use of reinforced, in particular glass fibre-reinforced (high performance) plastics can also be associated with disadvantages. Thus, glass fibres are abrasive and blunt the blades of wood processing tools. Further-more, the production of glass fibres and (high performance) plastics is energy-intensive and so environmentally unfriendly. Since high performance plastics have up to now only been able to be obtained from fossil raw materials, in this respect too they have a large carbon footprint and so are to be considered to be negative from an environmental point of view. In addition, high performance plastics are very expensive in comparison to bulk plastics.